The biogenesis of anthocyanins. V. Evidence for the mediation of pyrimidines in anthocyanin synthesis

Abstract

Anthocyanin synthesis in Spirodela oligorrhiza is inhibited by thiouracil and also by other compounds which interfere with pyrimidine or purine metabolism. These include (in order of increasing effectiveness) benzimidazole, 2,6-diaminopurine, quinine, azaadenine and azaguanine, the last-named compound being 650 times stronger as an inhibitor than thiouracil. With the exception of that due to benzimidazole, these inhibitions of pigment formation are partially or largely reversed by certain pyrimidines and purines. Another adenine derivative, 6-furfuryl-adenine or “kinetin” also causes clear inhibition. In the case of thiouracil, the inhibition is exerted in the light but not in the dark. The inhibition in the light is completely reversed by copper ions or by uracil or thymine, and partially reversed by adenine and hypoxanthine. However, plants preilluminated in a thiouracil solution produce no pigment in the dark even in the presence of uracil. The evidence, together with that previously presented, supports the idea that there are at least two stages in anthocyanin production: ( a) a light reaction in which a copper enzyme participates and which probábly involves the synthesis either of a nucleotide, or of one or more pyrimidines or purines, and ( b) a dark reaction utilizing the products of this light reaction for formation of anthocyanin.